Loft wiring advice please

Andyx · Nov 5, 2017

I am fitting a Nuaire Drymaster PIV into my loft space. I had it fitted in another house and it as it is max 15.3W and protected by a 1 Amp fuse was wired into the lighting circuit. I don't feel confident to do this through a junction box etc but there is loft light which I could use the wiring from easily - I just wanted to check is there a way I can do this without loosing the use of the light. As the the Drymaster has to stay on I assume I couldn't have both (without wiring direct from a junction box)?
cheers

telectrix · Nov 5, 2017

OK to wire to light circuit, but check if your neutral is at the light or at the switch.

jackhammerJIM · Nov 5, 2017

certain of a neutral at the light Tel

telectrix · Nov 5, 2017

jackhammerJIM said:
certain of a neutral at the light Tel

not necessarily. coming from a bedroom light it's usually easier to go to switch by hatch, then to light.

Dave OCD · Nov 5, 2017

telectrix said:
OK to wire to light circuit, but check if your ~~neutral~~ live and neutral supply is at the light or at the switch.

Edited for you Tel.

Dave OCD · Nov 5, 2017

telectrix said:
not necessarily. coming from a bedroom light it's usually easier to go to switch by hatch, then to light.

No I think he meant regardless of how it's been connected there will always be a neutral at the light Tel.

telectrix · Nov 5, 2017

DOH. after beer thinking. it'd a perm L he may not have at light. now i need to go to the back of the class.

Andyx · Nov 5, 2017

ok but I assume still I cant keep the light as well because of the switch as I want the drymaster switched on all the time?

MJPD29 · Nov 5, 2017

Is there a permanent and switched live at the light or just switched?

Dave OCD · Nov 5, 2017

If there's a live and neutral supply at the loft light switch you simply take a supply from the live side then connect via the fused connection unit - if they've supplied an unswitched one swap it for a switched unit to provide a means of isolation for the fan. This will have no effect on the light at all.

I2C · Nov 6, 2017

Simple answer - check to see where the permanent-line is located, at the switch or at the lamp (advice below):

Common Wiring (Loft Lamps)
In a loft, the permanent-line will often go to the switch first, with the lamp connected directly to the switch.
- Common way to tell: the neutral conductors (between supply cable & lamp cable) are usually joined in a connector-block inside the switch.

Alternative Wiring (Loft Lamps)
Sometimes the permanent-line goes to the lamp first, with a switch-wire run between the switch and the lamp.
- Common way to tell: The lamp will have a 'loop' connection which the permanent-line is connected to. There should also be visible brown-sleeving seen on some neutral-conductors in both the switch and lamp to indicate they are being used as line-conductors.

Side Note (Considerations)
- Make sure the circuit Ib (design current) is suitable for the additional equipment, small current-demands can add up quickly and result in potentially dangerous over-currents (and the circuit may have been modified in the past).
- Check the cable-calculations and voltage drops to be sure.
- Find the breaker you're using for the new equipment connection and label it in the consumer-unit for future reference.
- Carry out the necessary inspection & testing before going live.
- Remember that although the new equipment current-demand is low meaning that small-conductor sizes would be ok (under normal conditions), the protective device is calculated to protect the cables under fault-conditions and a small conductor size would not satisfy the requirements. Consider installing a FCU (Fused Connection Unit) in this case.

I hope this has helped. I've explained things simplistically just in case you're unsure but don't mean to seem rude (if it comes across that way). Always happy to answer any questions as best I can.

Andyx · Nov 6, 2017

I2C said:
Simple answer - check to see where the permanent-line is located, at the switch or at the lamp (advice below):

Common Wiring (Loft Lamps)
In a loft, the permanent-line will often go to the switch first, with the lamp connected directly to the switch.
- Common way to tell: the neutral conductors (between supply cable & lamp cable) are usually joined in a connector-block inside the switch.

Alternative Wiring (Loft Lamps)
Sometimes the permanent-line goes to the lamp first, with a switch-wire run between the switch and the lamp.
- Common way to tell: The lamp will have a 'loop' connection which the permanent-line is connected to. There should also be visible brown-sleeving seen on some neutral-conductors in both the switch and lamp to indicate they are being used as line-conductors.

Side Note (Considerations)
- Make sure the circuit Ib (design current) is suitable for the additional equipment, small current-demands can add up quickly and result in potentially dangerous over-currents (and the circuit may have been modified in the past).
- Check the cable-calculations and voltage drops to be sure.
- Find the breaker you're using for the new equipment connection and label it in the consumer-unit for future reference.
- Carry out the necessary inspection & testing before going live.
- Remember that although the new equipment current-demand is low meaning that small-conductor sizes would be ok (under normal conditions), the protective device is calculated to protect the cables under fault-conditions and a small conductor size would not satisfy the requirements. Consider installing a FCU (Fused Connection Unit) in this case.

I hope this has helped. I've explained things simplistically just in case you're unsure but don't mean to seem rude (if it comes across that way). Always happy to answer any questions as best I can.

Andyx · Nov 6, 2017

thanks much appreciated - I have checked the switch - here is a pic - there is sleeving on the blue so assume its the Alternative wiring described - does that mean I need to wire the drymaster to the lamp and not the switch?

[ElectriciansForums.net] Loft wiring advice please

westward10 · Nov 6, 2017

You will find the permanent live wherever that cable comes from either a light fitting, ceiling rose or junction box.

telectrix · Nov 6, 2017

the brown is permanent live. the blue with brown sleeve is switched live. neutrals will be blue with no sleeving.

Loft wiring advice please

Andyx

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telectrix

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jackhammerJIM

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telectrix

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Dave OCD

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Dave OCD

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telectrix

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Andyx

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MJPD29

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Dave OCD

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I2C

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Andyx

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Andyx

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westward10

telectrix

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